The 27-year-old midfielder has agreed a new two-year contract with the Frisian outfit.
Radomski joined Heerenveen from BV Veendam in 1997.
Meanwhile, Heerenveen have lost youth star Kassim Bizimana to FC Groningen.
The youngster - who was top scorer in Heerenveen's youth setup - has agreed a one-year deal with an option for another 12 months.
Groningen have also handed a new contract to goalkeeper Jeroen Lambers.
The 23-year-old, who is number two at The Oosterpark, has signed a 12-month extension - taking him to 2006.
